From Omuta in Northern Kyushu, Japan

Home , Akita Prefecture, Fukuoka Prefecture, Mie Prefecture, Northern Kyushu

Bull. Kitakyushu Mus. Nat. Hist., 9: 111-116. December 31, 1989

A New Eocene Lamnoid shark, Carcharodon nodai, from Omuta in Northern Kyushu, Japan

Yoshitaka Yabumoto

Kitakyushu Museum of Natural History, Nishihonmachi 3, Yahatahigashiku, Kitakyushu 805, Japan.

Abstract A new fossil lamnoid shark, Carcharodon nodai, is described here from a bed of the Late Eocene Manda Group in Omuta City, Fukuoka Prefecture, Japan. This species differs from other species of the genus Carcharodon in having the coarse serrations on the cutting edges of the crown and the anterior cutting edge is entirely convex in the outline.

Fossil teeth belonging to several speciesof the genus Carcharodon have been found from Oligocene to Pleistocene in Japan; Carcharodon angustidens from Oligocene in Kitakyushu (Uyeno et al., 1984, Yabumoto, 1987), C. sulcidens from Miocene in Mie Prefecture (Uyeno et al., 1980), C. akitaensis from Miocene in Akita Prefecture (Uyeno and Hasegawa, 1974), C. megalodon from Miocene to Pliocene in more than 40 localities ranging from Hokkaido to Miyakojima Island of the Ryukyu Islands (Goto, 1972; Uyeno elal., 1974; Uyeno et al., 1989) and C. carcharias from Pliocene to Pleistocene in Kochi, Shizuoka, Kanagawa, Chiba, Fukushima and Niigata Prefec ture (Uyeno et al., 1975; Uyeno and Matsushima, 1975, 1979; Kuga, 1985; Itoiga- wa et al., 1975; Sasagawa el al., 1989). In April, 1989, I visited Mr. Sakae Noda to investigate his collection of fossil shark teeth in Omuta City, Fukuoka Prefecture. In his collection, there was a peculiar fossil tooth belonging to the genus Carcharodon. Since I recognize that this specimen differs from other species of the genus Carcharodon, I describe here as a new species.

Acknowledgments

I like to express my sincere gratitude to Dr. Teruya Uyeno of National Science Museum for his invaluable advice and critical reading of the manuscript. I am very grateful to Mr. Sakae Noda for the donation of the specimen. I am also grateful to Dr. Ryuzo Toriyama and Dr. Masamichi Ota of Kitakyushu Museum of Natural History for their constant encouragement. 112 Yoshitaka Yabumoto

Class Chondrichthyes Order Lamniformes Family Lamnidae Carcharodon nodai sp. nov. (PI. 1, Fig. 3) Holotype specimen. KMNH (Kitakyushu Museum of Natural History) VP 100,145. This specimen was collected in 1978 and donated to the Kitakyushu Museum of Natural History by Mr. Sakae Noda in 1989. The specimen is consid ered to be a left lower jaw tooth. The basal part and the surface of the root and some parts of both cutting edges are missing.

Horizon. The Kattachi Formation in the Manda Group, Upper Eocene. Type locality. Kattachi (130°28'52*E, 33°00'45*N) in Omuta City, Fukuoka Pre fecture (Fig. 1). The locality is in the southern part of Fukuoka Prefecture. The

to Fukuoka

Fig. 1. Map showing the locality (X) of Carcharodon nodai sp. nov. Kattachi, Omuta City in Fukuoka Prefecture. New Eocene Lamnoid shark from Kyushu 113

Manda Group was first described by Nagao (1926) and has been studied by several geologists (e.g. Matsushita, 1949a; 1949b; Kihara, 1960; Kikuchi, 1963a; 1963b). According to Matsushita (1949a; 1949b), the Manda Group is predominantly sand-stone, of which, the rocks of the lower part (the Kattachi Formation) are glauconitic and fossiliferous, and those of the upper part (the Yotsuyama Formation) are fine-grained. The Kattachi Formation yielded marine molluscs, Crassatellites fnscus, Venericardia nipponica, V. mandaica and others (Matsushita, 1949a; 1949b).

Etymology. The specific name is taken from Mr. Sakae Noda who collected and donated the specimen.

Diagnosis. This species differs from other species of the genus Carcharodon in having combination of following characters, 1) the coarse serrations (6-7 indentations within 10 mm distance at the middle) on the both cutting edges, 2) the anterior cutting edge convex entirely (without concave part near the root) in the outline, 3) the lateral cusplets are present, 4) the crown thickness 27.2% of the crown length, 5) well developed neck region.

Description of the holotype specimen. The crown is strongly inclined to the rear and the angle between vertical line crossing the line between anterior and posterior ends of the crown base of the labial

10mm

Fig. 2. Carcharodon nodai sp. nov., holotype (KMNH VP 100,145) from Kattachi, OmutaCity in Fukuoka Prefecture. A, the labial surface; B, the lingual surface; C, the view of the anterior cutting edge. 114 Yoshitaka Yabumoto

labial (outer) surface lingual (inner) surface anteriorview Fig. 3. The method of the measurements of a fossil tooth of Carcharodon (from Yabumoto, 1987).

Table 1. The measurements of the holotype specimen of Carcharodon nodai sp. nov. from Omuta City, Fukuoka Prefecture.

a-b 54.4 mm b'-n 7.3 P 15.0+

a-b' 44.9 m-1 42.6 a-m 66.5

a-c 57.7 m-g 11.5 a-l 50.6

a-g 78.2 1-c 8.8 u 25° a-k 70.7 g-s 11.7

c-g 53.4 o 14.8

(outer) face and the line from the center of the line between anterior and posterior ends of the crown base to the apex is 25 degree (Fig. 3; u). Some parts of both cutting edges are missing, but the total number of serrations can be estimated. The anterior cutting edge is convex entirely in the outline. There is no concave part on the anterior cutting edge near the root. The posterior cutting edge is concave in the outline. Serrations are coarser in the middle parts of both cutting edges, and finer in the upper and lower parts. The anterior cutting edge has 6-7 indentations within each 10 mm distance at the middle part, 10 near the root and 9 close to the apex respectively. There are 38 serrations on the anterior cutting edge and the total is estimated to be 56. About 2 mm of the anterior cutting edge is missing at the middle in the position slightly closer to the apex of the crown. The posterior cutting edge has 6-7 indentations at the middle part and 10 indentations near the apex within 10 mm distance. Twenty four serrations are preserved on the posterior cutting edge and the total is estimated to be 43 or 44. About 4 mm of the posterior cutting edge New Eocene Lamnoid shark from Kyushu 115

is missing near the posterior cusplet. The lingual (inner) surface of the crown is convex and the central part is flattish. The labial surface of the crown is almost flat, but slightly convex near the apex. The basal part of the labial surface is deeply concave at the center and is convex at the anterior and posterior parts. A weak ridge runs upward from the center of the crown base. The base of serration along the anterior cutting edge is concave on the labial surface of the crown. The anterior cusplet has 9 serrations (5 serrations are coarse) on the anterior cutting edge, 8 fine serrations on the posterior cutting edge and one on the apex. Three serrations are preserved on both edges and one on the apex of the posterior cusplet. The tooth neck is wide at the central part and gradually narrows toward the anterior and the posterior. The lower part of the root is missing and the surface is entirely missing. The central part of the root appears to be convex.

Remarks The systematic considerations of the Cenozoic large shark teeth having serrated cutting edges are different in several workers (Cappetta, 1987). The disagreement is caused by the different selection of synapomorphy. In the present paper, these fossil sharks are placed in one genus, Carcharodon. Among the species ofthe genus, Carcharodon nodai is closer to Carcharodon angustidens (Agassiz) from the Oligocene sediments in the Ashiya Group, northern Kyushu (Uyeno et al., 1984; Yabumoto, 1987) in the size and having lateral cusplets, but differs from C. angustidens in the crown shape and having coarse serrations on the cutting edges. The outline of the anterior cutting edge is convex entirely without concave part near the root in C. nodai. In C. angustidens, the anterior cutting edge has a concave part near the root in the outline. C. nodai is also similar to Carcharodon landanensis Leriche (illustrated by Cappetta, 1987) from the Paleocene West Africa in the crown shape and having coarse serrations on the cutting edges, but differs from C. landanensis in the size and having fine serrations on the cutting edges near the root. The height ofthe crown is 54.4 mm in C. nodai. In C. landanensis, the height ofthe crown is about 2.5 mm and the serrations on the cutting edges near the root are coarse.

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Yoshitaka Yabumoto

Plate 1 Explanation of Plate 1

The holotype of Carcharodon nodai sp. nov. 1. The labial (outer) surface. 2. The lingual (inner) surface. 3. The view of the anterior cutting edge. All natural size. The natural form of the root is not clear (sec Figure 2) Yabumoto, Y. New Eocene Lamnoid shark from Kyushu Plate